Mechanism of Bax/Bak Activation During Apoptosis

细胞凋亡是一个重要的细胞死亡程序，它控制着正常的发育和维持内环境的稳定。 细胞凋亡的异常调节导致许多疾病，如神经退行性变、自身免疫 疾病和癌症。线粒体依赖途径是一条主要的凋亡途径，主要是 受Bcl2家族蛋白的调控和执行。Bcl2家族包括五个抗凋亡成员，两个 效应器蛋白Bax和Bak，以及八种仅支持BH3的促凋亡蛋白。它们控制着线粒体 线粒体外膜通透性(MOMP)这一中枢控制点的通路 到细胞凋亡。我们的长期目标是阐明信号通路和分子机制。 负责线粒体依赖的细胞凋亡，并对更多的发育提供积极影响 针对细胞凋亡相关疾病的有效和特异的治疗方法。虽然遗传和生化研究已经 BAX和BAK是MOMP的两个重要效应因子，BAX/BAK的作用机制由来已久 激活，通常被认为是细胞的生死开关，已经在 过去的二十年。目前的共识是，虽然所有促凋亡的BH3-Only蛋白都抑制了抗-BH3 BH3-Only蛋白中的一种--凋亡性的Bcl2蛋白直接参与并激活Bax和Bak 细胞凋亡。然而，在我们的初步研究中，我们提供的遗传证据表明，这种只有BH3的 Bax/Bak的激活和细胞凋亡不需要蛋白直接激活。相反，我们的结果 提示在仅BH3蛋白介导的抗细胞凋亡的Bcl2蛋白的中和作用下，Bax/Bak 经历一个依赖于膜的自发激活过程。根据我们的初步研究，我们 提出了一种新的Bax/Bak激活模型，该模型将主要从遗传学、细胞生物学和 生化方法。提出了以下三个目标。在目标1中，我们将研究 仅BH3蛋白和其他潜在的直接激活物在Bax/Bak激活中的作用 凋亡的Bcl2蛋白。在目标2中，我们将研究线粒体外膜在心肌梗死中的作用。 BAX/BAK激活的调节。在目标3中，我们将研究抗细胞凋亡的Bcl2蛋白的机制。 介导性抑制Bax/Bak的激活。总括而言，我们建议的研究可望澄清 Bax/Bak在细胞凋亡过程中的激活机制这项提议可能不仅会瓦解长期的 细胞凋亡研究中的谜团，也为治疗干预提供了新的靶点。

Apoptosis is an essential cellular death program that controls proper development and maintains homeostasis. Aberrant regulation of apoptosis contributes to many diseases, such as neurodegeneration, autoimmune diseases, and cancer. The mitochondria-dependent pathway is a major apoptotic pathway, and is primarily regulated and executed by the Bcl-2 family proteins. The Bcl-2 family includes five anti-apoptotic members, two effector proteins Bax and Bak, and eight pro-apoptotic BH3-only proteins. They control the mitochondrial pathway at the step of mitochondrial outer membrane permeabilization (MOMP), a central control point leading to apoptosis. Our long term goal is to elucidate the signaling pathways and molecular mechanisms responsible for mitochondria-dependent apoptosis, and provide positive impact on the development of more potent and specific therapies against apoptosis-related diseases. While genetic and biochemical studies have long established the role of Bax and Bak as two essential effectors of MOMP, the mechanism of Bax/Bak activation, commonly considered the life-to-death switch of the cells, has been intensively investigated in the past two decades. The current consensus is that while all pro-apoptotic BH3-only proteins suppress the anti- apoptotic Bcl-2 proteins, a subset of BH3-only proteins directly engage and activate Bax and Bak during apoptosis. However, in our preliminary studies, we provide genetic evidence suggesting that such a BH3-only protein-mediated direct activation is not necessary for Bax/Bak activation and apoptosis. Instead, our results suggest that upon the BH3-only protein-mediated neutralization of the anti-apoptotic Bcl-2 proteins, Bax/Bak undergo a membrane-dependent, spontaneous activation process. Based on our preliminary studies, we propose a new model of Bax/Bak activation, which will be examined primarily by genetics, cell biology, and biochemical approaches. The following three Aims are proposed. In Aim 1, we will examine the role of the BH3-only proteins and other potential direct activators in Bax/Bak activation following the inactivation of anti- apoptotic Bcl-2 proteins. In Aim 2, we will investigate the involvement of mitochondrial outer membrane in the regulation of Bax/Bak activation. In Aim 3, we will investigate the mechanism of anti-apoptotic Bcl-2 protein- mediated suppression of the Bax/Bak activation. Overall, our proposed studies are expected to elucidate the mechanism of Bax/Bak activation during apoptosis. This proposal may not only unravel one of the long standing mysteries in apoptosis research, but also provide novel targets for therapeutic intervention.